Scrolling input device

ABSTRACT

An input device may include an image sensor having an imaging surface comprising an array of pixels, and an optical waveguide layer carried by the imaging surface and having an exposed user surface and a first refractive index associated therewith. The input device may also include a substrate between the optical waveguide layer and the image sensor and having a second refractive index associated therewith that is lower than first refractive index. A collimation layer may be between the image sensor and the substrate. A light source may be configured to transmit light into the optical waveguide so that the light therein undergoes a total internal reflection. The optical waveguide may be being adjacent the imaging surface so that an object brought into contact with the exposed user surface disturbs the total internal reflection results in an image pattern on the imaging surface.

FIELD OF THE INVENTION

This invention relates to an input navigation device for computers,mobile phones, and the like, which is operated in a scrolling manner bymoving a finger on its surface, sometimes referred to as a fingermouse.

BACKGROUND OF THE INVENTION

A known fingermouse, or finger navigation device operated in a scrollingmanner is capacitance based. The capacitance based device generally doesnot operate satisfactorily if the finger is covered, for example, by aglove. Moreover, the size of the capacitance based device may be largein relation to other devices, such as, a mobile phone, and a personaldigital assistant (PDA).

An optical navigation device is also known, which operates on the sameprinciples as optical mice by comparing successive frames of an areaimage. The optical navigation device tends to be smaller, but there istypically a practical limit on reducing thickness because of the minimumfocal length to form an image on the surface of an image sensor.

There is therefore a need to provide a fingermouse navigation devicewhich can be manufactured with a reduced thickness. It is also desirableto manufacture such a device in a relatively simple manner and with arelatively low part count.

SUMMARY OF THE INVENTION

In view of the foregoing background, it is therefore an object of thepresent invention to provide an input device having a reduced thicknessand reduced part count, and that may be manufactured by a relativelysimplified process.

This and other objects, features, and advantages in accordance with thepresent invention are provided by a scrolling input device that mayinclude an image sensor having an imaging surface having an array ofpixels. The scrolling input device may also include an optical waveguidelayer over the imaging surface and having an exposed user surface. Thescrolling input device may also include a substrate layer between theoptical waveguide layer and having a lower refractive index than theoptical waveguide layer. A light source may transmit light into theoptical waveguide so as to undergo total internal reflection therein.The optical waveguide may be sufficiently close to the imaging surfaceso that an object brought into contact with the exposed user or contactsurface to cause frustrated total internal reflection may result in animage pattern on the imaging surface.

The optical waveguide layer and the substrate layer may be formed on topof the imaging surface. Alternatively, the optical waveguide layer andthe substrate may be formed integrally with the imaging surface.

Each of the optical waveguide layer and the substrate layer may includea polymer or a metal oxide. Suitable polymers may include polycarbonate,poly(methyl methacrylate) (PMMA), or epoxy. Preferably, each of theoptical waveguide layer and the substrate layer may have a thicknessless them 20 μm. This may allow the formation of a suitable image from afingerprint.

The light source may be a light-emitting diode. The light-emitting diodemay be attached to an angled extension of the optical waveguide, orformed integrally with the image sensor. Alternatively, thelight-emitting diode may communicate with the waveguide via a fiberoptic arrangement. A collimation layer, such as an array of microlensesor an array of micro optical fibers, may be between the image sensor andthe substrate, or may itself form the substrate.

Another aspect is directed to a method of providing a user input to anelectronic apparatus. The method may include providing an input deviceincluding include an image sensor having an imaging surface having anarray of pixels, an optical waveguide layer over the imaging surface andhaving an exposed user, or contact surface, and a substrate layerbetween the optical waveguide layer and having a lower refractive indexthan the optical waveguide layer. A light source may transmit light intothe optical waveguide so as to undergo total internal reflectiontherein. The optical waveguide may be sufficiently close to the imagingsurface so that an object brought into contact with the exposed usersurface to cause frustrated total internal reflection may result in animage pattern on the imaging surface.

The method may include bringing an object into contact with the exposeduser or contact surface, and moving the object across the exposed usersurface. The method may also include deriving user input informationfrom sequential frames of image formed at the imaging surface.

The object typically is a human finger. The object is preferably movedin a two-dimensional space, and the input information may be invectorial form.

A further aspect is directed to a method of making a scrolling inputdevice. The method may include providing a solid state image sensor chiphaving an imaging surface, and forming a substrate layer across theimaging surface. The method also may include forming an opticalwaveguide across the substrate layer so as to provide an exposed user orcontact surface. The substrate layer may have a lower refractive indexthan that of the optical waveguide. The method may further includeattaching a light source to the optical waveguide in a position totransmit light into the waveguide to undergo total internal reflection.The optical waveguide may be sufficiently close to the imaging surfaceso that an object brought into contact with the exposed user or contactsurface to cause frustrated total internal reflection results in animage pattern on the imaging surface.

Preferably, the substrate layer and the optical waveguide layer may eachbe formed by deposition such as spin coating deposition or chemicalvapor deposition. This advantageously simplifies manufacturing.

Another aspect is directed to an electronic apparatus including thedevice defined above. The electronic apparatus may, for example, be amobile phone, a PDA, a portable sound reproducing apparatus, a computer,a remote control, a game controller, or a mouse, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a finger navigating device inaccordance with the present invention;

FIG. 2 is a cross-section of part of the device of FIG. 1; and

FIG. 3 is a cross-section of the part of the device in FIG. 2 indicatingtypical dimensions.

FIG. 4 is a cross-section of part of a finger navigation device inaccordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention will now be described, by way of exampleonly, with reference to the drawings, wherein, like numbers refer tolike elements throughout, and prime notation is used to indicate similarelements in alternative embodiments. As seen in FIG. 1, the device 10 isoperated by sliding a finger 12 (or another object) across a top surfaceof the device 10. As in conventional devices, the movement is trackedand translated into vector information. However, in the presentembodiments no lens is used to form an image, and the surface can beplaced relatively close to the image sensor.

Referring to FIG. 2, the device 10 comprises an image sensor comprisinga single silicon chip 14 having a matrix of pixels indicatedschematically by reference numeral 16. The chip 14 may be any suitableform of integrated circuit image sensing chip, typically a complementarymetal oxide semiconductor (CMOS) sensor chip.

The chip 14 is overlaid by two layers. A first layer forms a substratelayer 18 of a relatively low refractive index. A second layer forms anoptical waveguide 20 of a relatively high refractive index.

Waveguide materials generally have a refractive index in the range 1.5to 2.0. The waveguide 20 may be formed, for example, from polycarbonate,which has a refractive index of approximately 1.59. The refractive indexof silicon is greater than 3, and, thus, forming the waveguide directlyon silicon generally does not provide total internal reflection.Therefore the waveguide 20 is separated from the surface of the chip 14by the substrate layer 18 for which a suitable material is PMMA, whichhas a refractive index of approximately 1.49.

In general terms, each of the layers 18 and 20 may be formed frompolymer or metal oxides. Suitable polymers may include polycarbonate,PPMA, and epoxy.

Silicon nitride has a refractive index of about 1.8. It would thus bepossible, therefore, to form a silicon nitride film directly on thesilicon to act as a substrate layer and to form the waveguide of ahigher-index material, such as a metal oxide. Thus the entire unit maybe manufactured in a fabrication process, for example, CMOS. In thepresent embodiment, however, the substrate layer 18 and the waveguide 20are formed by applying these layers to a previously fabricated chip byspin coating deposition or by chemical vapor deposition.

A light-emitting diode 22 is mounted to project light into the waveguide20. The LED 22 may be an infrared LED and emit infrared light, in whichcase no light will generally be visible in the area of the input device.Alternatively, the LED 22 may emit visible light, in which case a smallamount of visible light will generally leak in the vicinity of thefinger when the device is operated.

In this embodiment the LED 22 is attached to an angled projection of thewaveguide 20 such that the LED 22 emission axis is at right angles tothe waveguide. This feature allows the sensor chip 14 and the LED 22 tobe soldered at the same height. Alternatively, the LED could be formedon the chip itself, or the LED could be coupled to the waveguide viaoptical fiber.

When no finger is present on the device 10, light from the LED 22 istypically wholly within the waveguide 20 by total internal reflection.However, when a finger 12 is present, the ridges of the fingerprint arein contact with the surface and cause a frustration or disturbance ofthe total internal reflection as indicated at 23. Thus localizedscattering may result as indicated at 24. Thus a pattern is formed onthe image surface of the chip 14, forming an image which can be trackedas the finger moves. The image signal processing to track the movementand derive vector information is well understood from prior art devicesand need not be further explained.

For best performance, it is desirable that the object to be imaged is asclose as possible to the image sensor to achieve an acceptable picturefor tracking movement. The distance between the sensor and the imagedobject should typically be small in comparison with the spacing betweenfeatures of the object. As seen in FIG. 3, the spacing betweenfingerprint ridges is typically of the order of 200 μm, and anappropriate thickness for the layers 16 and 18 is <20 μm each.

The embodiments have the advantage of simplifying manufacturing. No lensis typically required, and the substrate and waveguide layers may beformed by layer deposition on top of a standard chip.

Modifications of the above embodiment may be made within the scope ofthe invention. For example, to enhance the quality of the image, anotherlayer 19, which acts as a collimator, may be added between the substrateand the sensor (FIG. 4). For example, the layer may be an array ofmicrolenses or micro optical fiber, or some other feature guiding lightstraight to the sensor. Alternatively, the collimating layer may,itself, form the substrate to the waveguide.

The embodiments thus provide a scrolling navigation device, which can bemade to a thickness, including any required encapsulation and contacts,less than 1 mm. This compares with prior art devices, such as >8 mm fora mechanical trackball and 3 mm for an optical (including a lens)fingermouse. The device is relatively inexpensive to manufacture, andtypically requires one chip, one LED, two thin layers of material, andno lens component. Moreover, manufacture generally includes only layerdeposition on a chip, with no assembly operations.

Because of the relatively small thickness of device, which can beachieved by way of the embodiments, the device is particularly useful inhand-held mobile devices, such as, phones, PDAs and personal musicplayers. The device is also useful in computers (especially laptops andnotebooks), remote controls, game controllers, and mice.

1-19. (canceled)
 20. An input device comprising: an image sensor havingan imaging surface comprising an array of pixels; an optical waveguidelayer carried by said imaging surface and having an exposed contactsurface and a first refractive index associated therewith; a substratebetween said optical waveguide layer and said image sensor and having asecond refractive index associated therewith that is lower than firstrefractive index; a collimation layer between said image sensor and saidsubstrate; and a light source configured to transmit light into saidoptical waveguide so that the light therein undergoes total internalreflection; said optical waveguide being positioned relative to theimaging surface so that an object brought into contact with the exposedcontact surface disturbs the total internal reflection resulting in animage pattern on the imaging surface.
 21. The device according to claim20, wherein said optical waveguide layer and the substrate are stackedon a top of said imaging surface.
 22. A device according to claim 20, inwhich the optical waveguide layer and the substrate are formed as amonolithic unit with said imaging surface.
 23. The device according toclaim 20, wherein said optical waveguide layer and said substrate eachcomprises at least one of a polymer and a metal oxide.
 24. The deviceaccording to claim 23, wherein said polymer comprises one ofpolycarbonate, PMMA, and epoxy.
 25. The device according to claim 20,wherein said optical waveguide layer and said substrate each has athickness less than 20 μm.
 26. The device according to claim 20, whereinsaid light source comprise a light-emitting diode (LED).
 27. The deviceaccording to claim 26, wherein said optical waveguide has a body portionand an angled extension extending outwardly from the body portion, andwherein said LED is coupled to said angled extension.
 28. The deviceaccording to claim 26, wherein said LED and said image sensor are formedas a monolithic unit.
 29. The device according to claim 26, furthercomprising an optical fiber; and wherein said LED is configured tocommunicate with said optical waveguide via said optical fiber.
 30. Thedevice according to claim 20, wherein said collimation layer comprisesone of an array of micro-lenses and an array of micro optical fibers.31. An input device comprising: an image sensor having an imagingsurface comprising an array of pixels; an optical waveguide layercarried by said imaging surface and having an exposed contact surfaceand a first refractive index associated therewith; a collimation layerbetween said optical waveguide layer and said image sensor and having asecond refractive index associated therewith that is lower than firstrefractive index; and a light source configured to transmit light intosaid optical waveguide so that the light therein undergoes totalinternal reflection; said optical waveguide being adjacent the imagingsurface so that an object brought into contact with the exposed contactsurface disturbs the total internal reflection resulting in an imagepattern on the imaging surface.
 32. The device according to claim 31,wherein said optical waveguide layer and the substrate are stacked on atop of said imaging surface.
 33. A device according to claim 31, inwhich the optical waveguide layer and the substrate are formed as amonolithic unit with said imaging surface.
 34. The device according toclaim 31, wherein said optical waveguide layer and said substrate eachcomprises at least one of a polymer and a metal oxide.
 35. The deviceaccording to claim 34, wherein said polymer comprises one ofpolycarbonate, PMMA, and epoxy.
 36. The device according to any claim31, wherein said optical waveguide layer and said substrate each has athickness less than 20 μm.
 37. The device according to claim 31, whereinsaid light sources comprise a light-emitting diode (LED).
 38. The deviceaccording to claim 37, wherein optical waveguide has a body portion andan angled extension extending outwardly from the body portion, andwherein said LED is coupled to said angled extension.
 39. The deviceaccording to claim 37, wherein said LED and said image sensor are formedas a monolithic unit.
 40. The device according to claim 37, furthercomprising an optical fiber; and wherein said LED is configured tocommunicate with said optical waveguide via said optical fiber.
 41. Thedevice according to claim 20, wherein said collimation layer comprisesone of an array of micro-lenses and an array of micro optical fiber. 42.A method of providing a user input to an electronic apparatuscomprising: providing an input device comprising an image sensor havingan imaging surface comprising an array of pixels, an optical waveguidelayer carried the imaging surface and having an exposed contact surfaceand a first refractive index associated therewith, a substrate betweenthe optical waveguide layer and the image sensor and having a secondrefractive index associated therewith that is lower than firstrefractive index, and a light source configured to transmit light intothe optical waveguide so that the light therein undergoes total internalreflection; the optical waveguide being adjacent the imaging surface sothat an object brought into contact with the exposed contact surfacedisturbs the total internal reflection resulting in an image pattern onthe imaging surface; and determining user input information fromsequential frames of an image formed at the imaging surface based uponan object to be brought into contact with and moved across the exposedcontact surface.
 43. The method of claim 42, wherein the object is movedin a two-dimensional space across the exposed user surface; and whereinthe user input information comprises vector information.
 44. A method ofmaking a scrolling input device comprising: providing an image sensorhaving an imaging surface; forming a substrate to be carried by theimaging surface; forming an optical waveguide to be carried by thesubstrate, the optical waveguide being formed to define an exposedcontact surface; the substrate being formed to have a lower refractiveindex than a refractive index of the optical waveguide; and coupling alight source to the optical waveguide to transmit light into thewaveguide to undergo total internal reflection; the optical waveguidebeing formed adjacent the imaging surface so that an object brought intocontact with the exposed contact surface causes a disruption in thetotal internal reflection to result in an image pattern on the imagingsurface.
 45. The method of claim 44, wherein providing the image sensorcomprises providing a solid state image sensor chip.
 46. The method ofclaim 44, wherein the substrate and the optical waveguide layer are eachformed by deposition.
 47. The method of claim 46, wherein the substrateand the optical waveguide layer are each deposited by at least one ofspin coating deposition and chemical vapor deposition.
 48. An electronicdevice comprising: an input device comprising an image sensor having animaging surface comprising an array of pixels, an optical waveguidelayer over said imaging surface and having an exposed contact surfaceand a first refractive index associated therewith, a collimation layerbetween said optical waveguide layer and said image sensor and having asecond refractive index associated therewith that is lower than firstrefractive index, and a light source configured to transmit light intosaid optical waveguide so that the light therein undergoes totalinternal reflection, said optical waveguide being adjacent the imagingsurface so that an object brought into contact with the exposed contactsurface disturbs the total internal reflection resulting in an imagepattern on the imaging surface.
 49. An electronic device according toclaim 48, wherein said electronic device comprises one of a mobilephone, a personal digital assistant (PDA), a portable sound reproducingdevice, a computer, a remote control, a game controller, and a mouse.